Liquid-raising apparatus



May 9, 1961 Filed July 20, 1956 J. J. WENT LIQUID-RAISING APPARATUS 2 Sheets-Sheet 2 United States Patent LIQUID-RAISING APPARATUS Jan J. Went, Arnhem, Netherlands, assignor to Stichting Reactor Centrum Nederland, s-Gravenhage, Netherlands Filed July 20, 1956, Ser. No. 599,098

Claims priority, application Netherlands July 23, 1955 1 Claim. (Cl. 103-233) The present invention relates to apparatus for pneumatically raising a liquid, in which upward flow of liquid is induced and maintained by passing gas upwardly through risers arranged in parallel into which the liquid is caused to flow.

Liquid-raising systems are known wherein upward current induction takes place under the action of a rising gas in one or more risers. For attaining a high tlow capacity it is advantageous to provide a plurality of risers through which the liquid flows in parallel and in each of which part of the current-inducing gas stream ascends, but if such a system is to operate elficiently it is necessary to take steps to ensure that the risers are uniformly loaded.

It is the main object of the present invention to provide liquid raising apparatus of the kind specified in which, when in operation, uniform loading of all the risers is ensured.

A further object is to provide such liquid raising apparatus which is self-regulating or self-stabilising with regard to fluctuations in the throughput of one or more of the risers occurring during operation.

A still further object is to provide liquid raising apparatus in which certain disturbances notably occurring when the apparatus is started, are counteracted.

Further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter, in the annexed drawings and in the appertaining claims. It should be understood, however, that the detailed description and drawings are presented by way of illustration and not of limitation.

According to the present invention we provide a liquidraising apparatus wherein the liquid is supplied to a plurality of risers for flow therethrough in parallel, and wherein each of the risers has a separate injector nozzle for the delivery of gas under pressure into the lower end of the riser and gas is supplied from a common source and at a constant pressure to all the nozzles so that upward flow of liquid is maintained in the risers, each injection nozzle being so dimensioned that if the rate of discharge of gas through that nozzle should change, the absolute value of the resulting change in the pressure drop across the nozzle is greater than the absolute value of the simultaneous resulting change in the hydrostatic pressure exerted in that riser by the liquid-gas mixture and equilibrium conditions are thereby restored.

When using a plurality of risers, it will be understood that if the rate of introduction of gas into one of the risers should for some reason, e.g., a temporary flow disturbance, begin to fall, the hydrostatic pressure exerted in that riser by the gas-liquid mixture will increase due to the increase inthe specific gravity of the gas-liquid mixture in that riser. Unless this specific gravity change is compensated, the pressure difference between the gas source and the interior of the riser will become smaller leading to a gradual decrease in the amount of gas supplied, and eventually to complete cessation of the upward 2,983,229 Patented May 9, 1961 flow in the riser in question. In an apparatus according to the present invention, when in operation, in the event of a reduced gas flow as aforesaid in one of the risers, the increase in the hydrostatic pressure is accompanied by a decrease in the pressure drop across the. appertaining injection nozzle which more than compensates for the specific gravity change so that the rate of flow of the gas automatically begins to rise again until the original state of equilibrium is regained. Should one of the risers momentarily receive too large an amount of gas the opposite changes in the specific gravity and the pressure drop will occur with the same result of restoring the equilibrium conditions.

Suitable dimensions of the injection nozzles may be readily determined experimentally for any individual case. The appropriate dimensions will depend on the dimensions of the apparatus, the-physical properties of the liquid to be raised, the gas to be used and the gas pressure.

While the automatic compensation obtainable as above referred to has been found adequate for controlling the fluctuations in the flow conditions encountered in normal operation, stronger fluctuations of the flow conditions inside the apparatus, which may notably arise when operation of the apparatus is started, cannot always be met in this way. Depending on the shape of the discharge chamber into which the upper ends of the risers discharge it may sometimes happen that one or more risers fail to operate when the apparatus is started, or even that liquid which has been raised flows back through one or more risers. This disadvantage may be obviated by temporarily blowing gas into the risers near their upper ends. If the liquid in a riser remains stationary, this measure will promote the formation of a rising current; if a downward current should have been formed in a riser, this measure will ensure the rapid formation of a liquid column of lower specific gravity due to the fact that gas bubbles. are dragged downwardly through the riser, so

' that the downward current is checked, and, subsequently,

the normal upward liquid current can be formed under the action of the .gas blown into the lower part of the riser.

As the temporary injection of gas into the upper parts of those risers which are already functioning normally does not occasion any difiiculties, it is preferred, if temporary introduction of gas into the upper end of one of the risers is necessary, to feed gas into the upper ends of the risers at the same time, and thereby to avoid the need for control valves or the like devices. 7

Furthermore it is preferred, for the introduction of gas near the upper ends of the risers, to use injection nozzles which, like the injection nozzles at the lower ends of the risers, are so dimensioned that if gas is fed thereto at a constant pressure and the rate of discharge of gas through that nozzle should change, the absolute value of the resulting change in the pressure drop across the nozzle is greater than the absolute value of the sim ltaneous resulting change in the hydrostatic pressure exerted in the upper part of the corresponding riser by the gasliquid mixture. This measure highly promotes a quick restoration of normal flow conditions in the corresponding riser, in a manner analogous to that described hereinbefore in connection with the special dimensioning of the lower gas injection nozzles.

If so desired, the supply of gas into the upper parts of the risers may be initiated automatically, by employing a feed control valve which is operated by impulses derived from elements responsive to the direction of flow in the risers.

As an alternative or additional measure for preventing liquid from flowing back in one or more risers if very marked fluctuations in the flow conditions occur within Fig. 1 is a vertical section through one apparatus;

Figs. 2 and 3 are horizontal and vertical sections, respectively, of details of the apparatus shown in Fig. 1 and Fig. 4 is a vertical section through a part of a modified apparatus.

The apparatus according to Figs. 1 to 3 comprises a number of tubular risers 1 arranged in parallel, a feed chamber 2 common to all the risers for the liquid to be raised and a discharge chamber 3 common to all the risers for the gas-liquid mixture that has been raised.

The apparatus is constructed so that in addition to its function as a current inducer for maintaining liquid in circulation, it can at the same time serve as a heat-exchanger.

The risers 1 pass through an upper pipe plate 4 and a lower pipe plate 5, the joints between risers and plates being liquid-tight; the plates 4 and 5 are fixed to a cylindrical casing 6, which surrounds the group of risers over the greater part of their height, said casing being provided at the top with a tubular feed passage 7 and at the bottom with a tubular discharge passage 8. The passages 7 and 8 may be connected into a circuit for a cooling or heating agent so that this may be circulated through the space 9 around the risers for heat exchange with the liquid circulating through the risers.

Each of the risers 1 is provided at the lower end with an injection nozzle '10. The injection nozzles 10 are in direct communication with a gas feed compartment 11, which is bounded by a cylindrical casing 12 fixed to the pipe plate 5 and integral with an end pipe plate 13. Through a number of openings 14 the gas feed compartment 1=1 communicates with a surrounding chamber 15 to which a gas feed conduit 16 is connected.

The feed compartment 2, the chamber 15 and the gas feed conduit 16 constitute a single casting 17, which is fastened by means of bolts 18 to the lower plate 5.

The dimensioning of the injection nozzles 10 is such that if a constant gas pressure is maintained in the gas feed conduit '16 and the apparatus is operating, an incidental change in the amount of gas flowing through any of the nozzles causes a change in the pressure drop across the nozzle the absolute value of which is greater than the absolute value of the simultaneous change in the hydrostatic pressure exerted in the corresponding riser 1 by the gas-liquid mixture. This ensures equal loading of the various risers and automatic compensation of flow variations, and hence operation of the apparatus at the maximum efiiciency.

In order to prevent liquid getting into and remaining in the gas feed compartment 11, as it might, particularly e.g. when the gas flow is shut oi, the injection nozzles 10 are placed as low as possible and are housed in recesses (see Figs. 2 and 3) in an additional plate 20. Each recess also locates a filling member 21 which cooperates with the appertaining nozzle and the plate to define a passage 22 for conducting gas downwardly to the'nozzle, which passage is so dimensioned that liquid present therein may freely flow back into the riser 1.

This latter measure is of special importance if the appara-tus is to be used for treating an aggressive or radioactive liquid, solution or suspension, such as, e.g., a suspension of uranium oxide or a similar fissile material in a moderating liquid such as common or heavy water,

4 which circulates through a nuclear reactor and through a heat exchanger.

In the apparatus illustrated provision is furthermore made enabling gas to be fed into the risers near their upper ends. 7 end with an injection nozzle 23. A gas feed compartment 24 bounded by a cylindrical casing 25 and an integral end pipe plate 26, is supplied through openings 27 from a surrounding chamber 28 fitted with a gas feed conduitv 29. The gas supply to the nozzles 23 takes place in exactly the same way as to the nozzles 10, there being an additional plate 30 which corresponds precisely with the plate 20. The discharge compartment 3, the feed chamber 28 and the gas feed conduit 29 constitute one casting 31, which is fastened to the pipe plate 4 by means of bolts 32. A feed control valve 40 is provided in conduit 29 in order to control the supply of gas to the injection nozzles 23 separately from the supply of gas to the lower injection nozzles 10. I

By temporarily supplying gas through the injection nozzles 23 marked disturbances of the operation of the apparatus may be rapidly eliminated in the manner described above.

Fig. 4 shows the upper part of a different form of apparatus. This apparatus may be regarded as identical with the apparatus according to Figs. 1 to 3 in regard to those of its parts which are not illustrated, but its upper part is constructed so that only a shallow body of liquid is maintained over the risers;'if liquid flows back in any of the risers a large amount of gas is drawn along, and as a result the downward current is checked and the normal rising liquid current becomes again established under the gas stream entering the bottom of the riser. The gas and liquid components of the mixture flowing out of the risers 1 are separated by means of a liquid separator formed by a bafiie plate 31. The separated liquid collects in the space 32 over the risers and is so discharged through the conduit 33 (which is fixed to the lateral extension of the upper pipe plate 4a) that only a shallow liquid layer is maintained over the risers. The separated gas passes into the space 34 over the liquid separator and subsequently discharges from the apparatus.

The collection space 32 for the liquid, and the gas collooting space 34, are formed in one casting 35, which is 1iafistened to the upper pipe plate 4a by means of bolts Example Use was made of an apparatus as illustrated in Figs.

l-3, which had the following characteristics:

Number of risers u 6 Inner diameter of risers mm 40 Height of risers mm 2500 Distance between lower injection nozzles and lower end of risers mm 50 Inner diameter of tubular part of lower injection nozzles mm 4 At room temperature water was raised by means of air, the pressure in the gas feed conduit 16 being maintained throughout the operation at 0.6 atm. gauge pressure.

With perfectly equal loads on all the risers a throughput of 24 mi /hr. was attained at an effcctive delivery head of 1.20 m.

I claim:

An apparatus for pneumatically raising a liquid, comprising a plurality of tubular risers arranged in parallel, a liquid feed chamber operatively connected to the bottoms of all the risers, a discharge chamber operatively connected to the tops of all the risers, a gas injection nozzle in the lower end of each riser, a first gas feed chamber communicating with each of said lower nozzles, a gas supply conduit communicating with said first gas feed Thus each riser is provided near its upper chamber, an additional gas injection nozzle in each of said tubular risers near the upper end thereof, a second gas feed chamber, separate from and independent of said first gas feed chamber, communicating with each said additional nozzle, a second gas supply conduit communicating with said second gas feed chamber, and control means in said second gas supply conduit for controlling the supply of gas to said additional gas injection nozzles separately from the supply of gas to said lower gas injection nozzles.

References Cited in the file of this patent UNITED STATES PATENTS 1,034,703 Freeman Aug. 6, 1912 1,035,955 Freeman Aug. 20, 1912 1,076,600 Morison Oct. 21, 1913 

